1. Field of the Invention
The present invention relates to a waterproof structure of an electrical junction box which is to be mounted on a vehicle and prevents entry of water through a clearance between a cover and a case of the electrical junction box.
2. Related Art
FIGS. 6 and 7 show a conventional waterproof structure of an electrical junction box (see Unexamined Japanese Patent Application Hei-8-288667).
In FIG. 6, reference numeral 30 designates a cover formed from synthetic resin; 31 designates a waterproof packing; and 32 designates a case formed from synthetic resin. A relay connection section 33, principally, is housed within the case 32. An electrical junction box 34 is a generic name for a relay box, an unillustrated fuse box, or an unillustrated junction box. Resilient lock members 35, each paired with a lock frame section 36, are provided on opposite sides of the electrical junction box 34, thereby locking together the cover 30 and the case 32.
A recess 37 (see FIG. 7) for receiving the waterproof packing 31 is formed along and over the entire outer peripheral lower edge of a skirt section of the cover 30. The recess 37 is defined by an exterior hood wall 38 and an interior elongated wall 39 (see FIG. 7). When the waterproof packing 31 is fitted into the recess 37 and the cover 30 is placed on the case 32, an upper end 40 of the case 32 is brought into pressing contact with the waterproof packing 31, thus materializing primary waterproof sealing.
A stepped section 41 (see FIG. 7) is formed along the skirt section of the hood wall 38 of the cover 30. A flange section 42 to be brought into contact with the stepped section 41 is projectingly formed along the case 32. When the cover 30 is placed on the case 32, the stepped section 41 is brought into contact with the flange section 42, thus materializing secondary waterproof sealing of the electrical junction box 34 (see FIG. 6). The electrical junction box 34, which houses electronic devices susceptible to water or dusts, requires a double-waterproof structure.
In the above-described conventional structure of the electrical junction box, the stepped section 41 of the cover 30 is in plane contact with the flange section 42 of the case 32. Hence, the contact is effected by weak forces. For example, if the cover 30 is slightly warped, a horizontal clearance will arise between the stepped section 41 and the flange section 42, thus resulting in a fear of water or dusts entering the waterproof packing 31.
A vertical clearance 44 arises between the flange section 42 and the interior surface of a skirt wall 43 continuing from the stepped section 41. There is apprehension that, for example, when the electrical junction box is exposed to high-pressure water at the time of engine cleaning, the water easily breaks through the secondary waterproof mechanism (materialized by the stepped section 41 and the flange section 42) and reaches the waterproof packing 31 by way of the vertical clearance 44. However, the vertical clearance 44 is important for smooth fitting of the cover 30 to the case 32.
The present invention has been conceived in view of the foregoing problem, and the object of the present invention is to provide a waterproof structure of an electrical junction box which is improved in preventing entry of water and dust into the electrical junction box by way of a clearance between a stepped section of a cover and a flange section of a case, and which can prevent entry of high-pressure water into the electrical junction box by way of a clearance between a skirt wall of the cover and the flange section of the case.
To achieve the object, the present invention provides a waterproof structure of an electrical junction box which renders the electrical junction box waterproof by bringing a stepped section of a cover into contact with a flange section of a case, wherein
a protuberance to be brought into pressing contact with the stepped section or the flange section is formed along the periphery of the stepped section or the flange section.
Preferably, the leading edge of the protuberance is brought into line contact with the flange section or the stepped section in order to provide effective sealing.
Further, preferably, in order to provide effective sealing, a skirt wall is formed so as to extend downwardly from the stepped section, and a second skirt wall is formed so as to extend from the flange section along the skirt wall.